what kind of skis do you have? also what kind of boots do you have? The pain is most likely because of your boots if they're 4 years old, I would be surprised if the liners weren't super packed out(the padding is worn down and thin) and that is what a lot of pain can come from. I used to hate going skiing because my legs would hurt so much because of my boots, but now with new(good) boots my legs feel great. If you have stiff skis, then that would be why you can't press very high. also just to clarify you are talking about this kind of tail press
if you are, then you most likely won't be able to get that high, he is in powder so it makes pressing that far back a lot easier than on hard pack.